The heart is composed of the cardiac muscle, through the cardiac muscle beats in a regular manner, the heart can be like a pump to transmit the blood to whole body. The cardiac muscle not only can contract, but also can generate conduct current. The organism itself is a good conductor, the current generated from the changes of the cardiac action potential of cardiac conduction fibers, will spread to the whole body from the heart, but different parts of the body include different conducting cells and patterns, the current distribution is not the same.
Different potentials and the sizes of the waveform recorded by different electrodes are called leads. Any two electrodes can be formed as a lead. Metal electrode can be disposed on the organism body limbs, chest, endocardial or epicardial surface for guiding the current of the heart. It is called epicardial electrogram that records the electric signals on the cardiac epicardial surface by the electrodes.
However, the equipment for detecting epicardial or endocardial signals, is fairly complex. The equipment is usually only used to detect a human endocardial electrogram, because the heartbeat of a small animal is very fast and heart volume is very small. It is difficult to detect those in small animals.
Taking a mouse as an example, the method of the prior art to detect the electrophysiological signal of the mouse is to use a very small electrical catheter through a vein or artery to check. However, the technology is very difficult, and it requires large equipment, such as electrical stimulation systems, signal reception and display imaging system, the catheter connection system. The signal is endocardial signals, instead of the epicardial signals. The large equipment is not only expensive, bulky, but also the catheter is easy to damage, and the information collected is limited.